basic compressor knowledge
TRANSCRIPT
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Basic compressor knowledge
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The Process Of Gas
Compressors
kinds of gas compressors
principle of reciprocating compressors
Effect of clearance
Multilevel compress with intercoolers
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Types of gas compressors
There are two general types compressors
Reciprocating compressor
For high pressures and low-volume flow
rates..
Rotative compressor
For lower pressures and high-volume flow
rates.
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Types of gas compressors
Air compressor
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Types of gas compressors
Reciprocating compressor
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Types of gas compressors
Refrigerator compressor
Motor
Compressor
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Types of gas compressors
Refrigerator compressor
Motor
Compressor
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Types of gas compressors
Refrigerator compressor
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Types of gas compressors
Icebox compressor
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Types of gas compressors
Centrifugal rotative compressor
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Types of gas compressors
Centrifugal rotative compressor
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Types of gas compressors
Axis flow rotative compressor
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principle of reciprocating compressors
Wc
H1
H2
Q?
V
p
P1 1
P2 2
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principle of reciprocating compressors
v
p
P1 1
P22T 2s2n
s
T
P1
1P2
2s
2n
2T
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principle of reciprocating compressors
1.The principle
Notice that there will be a difference between the work
necessary to compress the gas from states 1 to state
2 and the total work of process.
Wcs>Wcn>WcT
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principle of reciprocating compressors
2.The work of compressor
Adiabatic compressor
11
)(1
1
1
21112212,
k
k
gscp
pTRk
kvpvpk
khhw
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9-2. The principle of reciprocating
compressors
2.The work of compressor
Isothermal compressor
1
21
1
21, lnln
p
pTR
v
vTRw ggTc
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9-2. The principle of reciprocating
compressors
2.The work of compressor
Polytropic compressor
11
)(1
1
1
211122,
n
n
gncp
pTR
n
nvpvp
n
nw
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principle of reciprocating compressors
2.The work of compressor
Tns
Tns
Tcncsc
vvv
TTT
www
,2,2,2
,2,2,2
,,,
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Effective Absolute pressure
atmospheric
pressure
absolute
pressure
effectivepressure
total pressure
pressure = 0
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Effect of clearance
Wc
V
p
P1 1
P2 2
H1
H2
4
3
1.Clearance
f
g
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Effect of clearance
Wc
V
p
P1 1
P2 2
H1
H2
4
3
1.Clearance
f
g
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Effect of clearance
2.The work of compressor Polytropic compressor
1)(1
11
11
1
1
2411
1
4
344
1
1
211
343112,
n
n
n
n
n
n
gfgfnc
p
pVVp
n
n
p
pVp
n
n
p
pVp
n
n
w
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Effect of clearance
2.The work of compressor Polytropic compressor
)1(1
11
1
1
1
1
21,
nn
g
n
n
nc
TmRn
n
ppVp
nnw
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Multilevel compress with intercoolers
1.SystemCooling water
Low pressure gas
1st-stage
compression
2nd-stage
compression
Intercooler
High pressure gas
1223
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Multilevel compress with intercoolers
2.Diagram
V
p
P1
1
P2
2
3
e
g
f2
3
Pm
3T
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Multilevel compress with intercoolers
3.The work of compressor
2)()(1
1)(1
1)(1
1
2
3
1
1
2
1
1
2
32
1
1
21
,,
'
n
n
n
n
g
n
n
gn
n
g
hclcc
p
p
p
p
TRn
n
p
pTR
n
n
p
pTR
n
n
www
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Multilevel compress with intercoolers
312 pppp m
2
3
1
2
pp
pp
3.The work of compressor
m
m
m
m
p
p
p
p
p
p
p
p 1
12
3
1
2
..........
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Multilevel compress with intercoolers
3.The work of compressor
)1(1
1
1
n
n
gc TRn
nmw
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Absolute pressure8 bar
Atmospheric pressure
1 bar
Effective pressure
7 bar
Effective pressure
The effective pressure is the differencebetween absolute pressure and
atmospheric pressure
It is the pressure available to deliver work
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Free Air Delivery
Free Air Delivery :
is the measured real
delivered volume of air
(in l/s or m/min or cfm)at the same conditions of
pressure and temperature
at the air inlet
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Free Air Delivery
FAD is not equal to the displacement
volume of the compressor element,
because internal losses in the element
(leaks to air inlet)
FAD is independent from the ambient
conditions (temperature & pressure)
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Compression principle
1
Volume
Pressure
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Compression principle
1
Volume
Pressure2
Compression
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Compression principle
1
3
Volume
PressureDischarge 2
Compression
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Compression principle
1
3
4
Volume
PressureDischarge
Pressurereduction
2
Compression
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Compression principle
1
3
4
Volume
PressureDischarge
Suction
Pressurereduction
2
Compression
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Compression principle
1
3
4
Volume
Pressure
Suction Volume
Stroke Volume
Discharge
Suction
Pressurereduction
2
Compression
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Screw Compressor
Introduced in 1958 by Atlas Copco
Male and female rotors move towards
each other, while the volume between
them and the housing decreases.
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Screw Compressor Screw profile improved in 1966
Symmetrical screw was changed in an
asymmetrical helical profile
10% more efficiency
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Compression principle
Compressionstart
Compression
Suction
Deli
very
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Pressure Ratio
Each screw element has a fixed,integrated pressure ratio
This depends on :
length of the rotors Pitch of the screw
form of the discharge port
Best efficiency is reached when thepressure ratio is adapted to the required
working pressure
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Advantages screw compressor
High shaft speeds and large flow rate :
gives small exterior dimensions
Simple and strong design :
no valves and seals reliable and
maintenance friendly
small dirt particles improve the sealing and
the efficiency almost pulsation free air
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Advantages screw compressor
Low wear :
guaranteed long life time and constant
capacity
life time is determined by the bearing wear
Absolute oil free design possible
No inertia forces
vibration free operation
high speeds possible
big power possible
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Disadvantages screw compressor
Lower efficiency because of internal leaks
High quality bearing of the rotors required
rotor clearances are small
axial bearings needed
Higher noise level (high frequency)
High quality finishing of the rotors required
expansion of rotors through heat results in
blocked elements
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Oil injected screw compressors
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Oil injected screw compressors
Oil is used for :
Cooling : compression heat is absorbed by
the oil
Lubrication of rotors, bearings, gears
Sealing between rotors and rotor and
housing
Corrosion protection of the internal metalparts
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Oil injected screw compressors
Oil is injected in the bottom of the rotor housing,
on the bearings and gears
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Oil injected screw compressors
Only one rotor is driven, this rotor then
drives the other one :
old XAS 90 : female driven rotor
all other compressors : male driven rotor
When required a gear box or drive belt
brings the compressor element to the
correct speed
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Oil Free screw compressor
No oil is injected in the air Complete separation of oil used for
lubrication of bearings and gears
An external synchronizing gear is usedto synchronize the rotors
no contact between rotors and housing
Pressure ratio is limited by thetemperature difference between the
intake and the discharge
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Oil Free screw compressor
Synchronizing Gear
Seal rings
Oil gallery
Water jacket cooling
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Comparison
Separate oil system
with oil pump
No oil separators
required Compression of
gasses is possible
Special coating onthe rotors
Water jacket cooling
Integrated oil system
without oil pump
Oil separators
needed Not suitable for oil
aggressive gasses
No coating on therotors
Oil cooling
Oil Free Oil Injected
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Comparison
Seal rings on the
shafts
Synchronization
gears High speed, high
noise
High temperature Max. pressure ratio
is low (1:4)
No internal sealing
One rotor drives the
other
Lower noise due tolower speed and oil
Low temperature due
to oil cooling High pressure ratio
possible (1:13)
Oil Free Oil Injected
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Compressor regulating system
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Compressor running condition
Four major running conditions : NO-LOAD
Machine started, minimal pressure build-up
UNLOADReceiver tank pressurized, no air
consumption
LOAD
Receiver tank pressurized and airconsumption
BLOW-DOWN
Machine stopped, blow-off of air pressure
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Compressor systems
Four major components :
Air system
Oil system
Regulating system
Electrical system
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Air filterCompressorElement(AFCE)(with
vacuator valve VV, Safety Cartridge SC and
vacuum indicator VI)
Unloading Valve (UV)
Compressor Element (CE)
Temperature Switch (TS)
Check Valve (CV)
Air Receiver(AR)
Non Return Valve
Minimum Pressure Valve(MPV)
Air Outlet Valve (AOV)
Air system
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Air filter
Filtration of the inlet air in 3 stages :
centrifugal dust separation
paper filter element
safety cartridge (optional)
Vacuum indicator gives an indication
when the pressure drop over the filter
element is too high filter element needs
to be replaced
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Air filterAir inlet Centrifugal separation
Dust
Filter element
to compressor element
Vacuum indicator
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Unloading valve
Opens and closes the air inlet to the
compressor element.
Open position at load condition
=> Air consumption
Closed position at no load condition
=> No air consumption.
Control of the valve by regulatingpressure.
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Compressor element
Oil is injected in the air and compressed
to the pressure as set by the regulating
valve.
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Compressor element
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Compressor element
Oil
Oil
Air/Oil
Air inlet
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Air receiver / Separator
Air/Oil
Centrifugal separation
Separator element
Air outlet
Mi i l / l
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Minimum pressure valve / nozzle
Guarantees a minimum pressure in the oil
separator (approx. 3.5 bar)
Minimum pressure is required toguarantee an continuous oil supply to the
element.
N l / Mi i l
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Nozzle / Minimum pressure valveMINIMUM PRESSURE VALVE
NOZZLE
Oil filt
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Oil filter
Dirty Oil Filtered Oil
By-pass valve
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Compressor element
Oil
Oil
Air/Oil
Greasing to the bearings
Air inlet
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Regulating system
Unloading valve
Speed regulator
Blow-down valve
Safety valve
Regulating system (Series 6)
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Regulating system (Series 6)
Regulating Valve
Unloading Valve
Speed Regulator
Safety Valve
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Unloading valve
Opens and closes the air inlet to the
compressor element.
Open position at load condition
=> Air requirements
Closed position at no load condition
=> No air requirements
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Unloading valveRegulating pressure Air inlet
Vent Hole
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Unloading valveLOAD UNLOAD
Re
gulatingpressure
Air inlet
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Blow-down valve
Blows off the air receiver pressure oncethe compressor has shut-down
=> this to depressurize the receiver tank
Integrated in the unloading valve
Blow down valve
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Blow-down valve
blow-down
valve
Receiver pressure
blow-off hole
Air inlet
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Blow-down valveLOAD / UNLOAD BLOW-DOWN
Receiver pressure
Receiver pressure return
after shut-down
Blow-off
receiver pressure
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Safety valve
Blows off the air receiver pressure oncethis pressure raises above the design
pressure.
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Electrical system
Battery voltage : 12 or 24 V Starting system
cuts-out starter motor when engine is running
avoids cranking when receiver tank ispressurized
Safety shut-downs
Instrument indications
S f h d
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Safety shut-downs
Compressor : Compressor element outlet temperature
Engine :
Coolant temperature Coolant level
Oil pressure
Fuel level Emergency stop
S f t h t d
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Safety shut-downs
All safety shut-downs are Normal Closedswitches
Fail safe as a loose wire will result in a shut-
down
Good electrical contacts are important
PARTS OF SERVICE COMPRESSOR
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PARTS OF SERVICE COMPRESSOR
Air treatment options
Lubricator Aftercooler
Water separator
Fine filters PD / QD
Re-heater
Air treatment options
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Air treatment options
Aft l W t t
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Aftercooler - Water separator
The aftercooler is a heat exchanger,which cools the hot compressed air to
precipitate the water that otherwise would
condensate in the air hose.
The outlet temperature is ambient + 7C.
It is followed by a water separator that
separate the condensate and drains it
Used for : sandblasting, fibre optic cable
steering, pipe cleaning
Aft l W t t
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Aftercooler - Water separator
Water separator
Aftercooler
Fi filt PD / QD
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Fine filters PD / QD
PD filter will separate oil and solidparticles.
QD filter or carbon filter will separate oil
and water vapour. Air becomes technically oil free.
Only 0.003 ppm oil is available in the air
outlet
Fi filt PD / QD
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Fine filters PD / QD
PD filter
QD filter
R h t
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Re-heater
The re-heater is a heat exchanger, whichwarms up the compressor outlet air to
ambient + 60C.
The water and oil will be vaporized resulting
in hot and dry air, this avoids condensate
problems.